Phospho-signalling deregulation of the mTOR pathway in fibroblasts from LRRK2 Parkinson s patients

Activating mutations at the leucine-rich repeat kinase 2 (LRRK2) gene are the most frequent genetic cause of Parkinsons Disease (PD). Using in-depth mass-spectrometry, here we analysed the impact of LRRK2 mutations on the proteome and phospho-proteome of skin fibroblasts from a large LRRK2 clinical cohort from Spain. The cohort encompassed G2019S LRRK2-associated PD (L2PD) (n=15), G2019S LRRK2 non-manifesting carriers (L2NMCs) (n=13), idiopathic PD (iPD) (n=12), and control subjects (n=14) (total n=54). The proteome analysis revealed 89 differential proteins in G2019S L2PD (58 down/ 31 up) and 168 in G2019S L2NMCs (127 down / 41 up) compared to controls. Most of these proteome changes involved deficits in proteins related to mitochondrial energy and ribosomal protein synthesis. At the phospho-proteome level, we identified 394 differential phospho-sites in G2019S L2PD (188 hyper / 206 hypo), 367 in G2019S L2NMCs (215 hyper / 152 hypo), and 428 in iPD (214 hyper / 214 hypo) compared with controls. These phospho-proteomic changes included hyper-phosphorylated proteins associated with the mTOR and Rho GTPase pathways. Notably, the top hyper-phosphorylated hit in G2019S carriers was pThr37/46 4E-BP1, a key effector of the mTOR pathway controlling protein synthesis, and this protein was also deregulated in iPD. In summary, our study uncovers peripheral deregulation of mTOR phospho-signalling associated with LRRK2 mutations, which is related to deficits in mitochondrial and ribosomal proteins, and affects converging pathways altered in iPD.